1. Field of the Invention
The present invention relates to a pressure sensing semiconductor device which is package sealed by molding resin material. The present invention also relates to a method of manufacturing such a mold-packaged pressure sensing semiconductor device.
2. Description of the Background Art
As a package for package sealing a pressure sensing semiconductor device, a metal package and a hollow resin package, which is formed by molding resin, are in wide use in the semiconductor industry, the reason being that the metal packages have an excellent endurance against environmental disturbances and the hollow resin packages are cost-effective although less reliable under adverse environmental conditions. The hollow resin packages are employed on the premise that a pressure sensor of a semiconductor device operates under relatively clean measuring conditions in detecting atmospheric and other pressures. Thus, behind the popular use of the hollow resin packages are their cheapness which weighs more importance than the device reliability to environmental disturbances. Still, small wonder that the weakness in the device reliability does remain as a problem, especially in connection with thin bonding wires, typically gold and aluminium, which connect an internal element (i.e., a sensor element) and external leads being unmolded.
Some seek a solution not in the hollow resin packages but in the mold packages, a package which is popular in the IC industry. While the mold packages promise an increased reliability of the bonding wires, molding technique needs to be improved because a pressure receiving part for detecting pressure, generally referred to as a silicon diaphragm, must be left unmolded. To prevent molding resin from flowing into the silicon diaphragm, special packaging considerations are necessary in determining the configuration of a metallic mold and the structure of the sensor element.
For all the improvement in package sealing, a mold-packaged semiconductor device for detecting pressure is faced with a number of difficulties. For instance, the very improvement adversely affects the design simplicity of the metallic mold. Equally problematic, since the pressure receiving surface of the sensor element is extremely small, to perfectly inhibit molding resin flow into the pressure receiving surface is almost impossible. These difficulties have been discouraging use of mold-packaged pressure sensing semiconductor devices. Mold-packaged pressure sensing semiconductor devices which are relatively reliable under hard environmental conditions and extremely cheap to fabricate are yet to be seen.